ML20151L331

Masonry Wall Design, Technical Evaluation Rept

ML20151L331
Person / Time
Site:	Nine Mile Point
Issue date:	11/04/1985
From:	Carfagno, Con V, Friolo S, Triolo S CALSPAN CORP.
To:	NRC
Shared Package
ML17058A519	List: ML20151L331
References
CON-NRC-03-81-130, CON-NRC-3-81-130 IEB-80-11, TAC-42884, TER-C5506-238, NUDOCS 8512100109
Download: ML20151L331 (24)

Text

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ATTACHMENT TECHNICAL EVALUATION REPORT NRC DOCKET NO. 50-220 FRC PROJECT C5506 NRC TAC NO. 42884 FRC ASSIGNMENT 6 NRC CONTRACT NO. NRC-03 81 130 - FRC TASK 238 MASONRY WALL DESIGN NIAGARA MOHAWK POWER CORPORATION NINE MILE POINT NUCLEAR STATION UNIT 1 TER-C5506-238 Prepared for Nuclear Regulatory Commission FRC Group Leader: V. Con Washington, D.C. 20555 NRC Lead Engineer: N. C. Chokshi November 4, 1985 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa-ratus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.

Prepared by: Reviewed by: Approved by:

W N Y4 rt [n kDepartm(nt Head

1. 5" l ~PrinciSal A t o Group' Leader l Date: ll /' l Y Date: Hl00lf5 Date: ^~**W

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- FRANKLIN RESEARCH CENTER l

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[- DIVISION Of: ARVIN/CALSPAN '

RACE $79ttTS.PMitADELMelA.PA 8910$

TER-C5506-238 j i

CONTENTS Section Title Page 1 INTRODUCTION . . . . . . . . . . . . . I 1.1 Purpose of Review . . . . . . . . . . . 1 1.2 . Generic Issue Background . . . . . . . . . I 1.3 Plant-Specific Background . . . . . . . . . 1 2 EVALUATION CRITERIA. . . . . . . . . . . . 4 3 TECHNICAL EVALUATION . . . . . . . . . . . 5 3.1 Evaluation of Licensee's Criteria . . . . . . . 5 3.2 Evaluation of Licenaae's Approach to Wall Modifications . -11 4 CONCLUSIONS. . . . . . . . . . . . . . 12 5 REFERENCES . . . . .- . . . . . . . . . 13 APPENDIX A - SGEB CRITERIA FOR SAFEIY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH (SGEB]-OF THE NRC)

APPENDIX B - SKETCH OF TYPICAL WALL MODIFICATION i

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TER-C5506-238 FORDORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Cow.ission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for' technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by the NRC.

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1. INTRODUCTION i

.1.1 PURPOSE OF REVIEW The purpose of this review is to provide technical evaluations of licensee responses to IE Bulletin 80-11 (1]* with respect to compliance with the Nuclear Regulatory Comunission (NRC) masonry wall criteria. In addition, if a licensee has planned repair work on masonry walls, the planned methods and procedures are to be reviewed for acceptability.

1.2 GENERIC ISSUE BACKGROUND In the course of conducting inspections at the Trojan Nuclear Plant, Portland General Electric Company determined that some concrete masonry walls <

did not have adequate structural strength. Further investigation indicated that the problem resulted from errors in engineering judgment, a lack of established procedures and procedural details, and inadequate design criteria. Because of the implication of similar deficiencies at other

! operating plants, the NRC issued IE Bulletin 80-11 on May 8, 1980.

IE Bulletin 80-11 required licensees to identify plant masonry walls and 1- their intended functions. Licensees were also required to present reevaluation criteria for the masonry walls with the analyses to justify those criteria.

If modifications were proposed, licensees were to state the methods and schedules for the modifications.

1.3 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Niagara Mohawk Power Corporation performed an analysis of the masonry izalls at the Nine Mile Point plant. It then provided the NRC with documents (2, 3] describing the status of masonry

! walls at Nine Mile Point Nuclear Station Unit 1. The information in these documents was reviewed and a request for additional information was sent to the Licensee on April 22, 1982, to which the Licensee responded (4]. In conference calls on October 21, 1982 and December 14, 1982, the Licensee

• Numbers in brackets indicate references, which are cited in Section 5.

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TER-C5506-238 agreed to furnish additional information. Subsequently, Niagara Mohawk determined that a reanalysis of the walls was in order due to the lack of consideration of high energy line break effects in the first analysis and a revised technical position on Dur-O-Wal. A meeting was held on April 27, 1983 i 4

between Niagara Mohawk and the NRC so that the Licensee could provide

additional information regarding the status of its masonry wall review, i previous NRC questions, and the design criteria for the wall reanalysis. As a result of this meeting, the NRC indicated additional questions on the l

,t reanalysis criteria in the meeting minutes dated May 13, 1983. In response, Niagara Mohawk submitted the document dated' June 2.4, 1983~[5] containing the j

" Design Criteria for the Re-Analysis'of Safety-Related Masonry Walls, Nine Point Mile Point Unit 1." Finally, the Licensee provided the document dated June 21, 1984 [6] containing more information on the masonry wall reanalysis and the Licensee's test program.

The Licensee identified 75 safety-related masonry wall systems at Nine l Mile Point Unit 1. A wall system was defined as a ' single wall or combination of walls in close proximity to each other. These walls function as partition, fire, or radiation shield walls. Only 10% of the walls have equipment  ;

attached to them.

All walls have extra-heavy Dur-O-Wal joint reinforcement, and most also-i have vertical reinforcement with the reinforced cells filled with grout. The majority of walls are single wythe and partially grouted, but about 25% are of solid (i.e., fully grouted or solid block), multi-wythe construction. Five ,

wall systems were laid in a stack bond.

Masonry walls were constructed of either normal concrete blocks with a density between 130 and 145 pounds per cubic foot or light weight concrete block at 105 pounds per cubic foot. When the material strength specification

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l was not available, the Licensee used a. masonry compeessive strength (f'm) of

{ 700 psi, which is the minimum value given in Table 4.3 of ACI 531-79 [8].

I This value corresponds to a masonry unit test strength of 1000 psi and Type N I mortar. All Dur-O-Wal has a yield strength of 40 ksi.

In its initial analysis of masonry walls, the Licensee determined that i six walls required modifications. In the subsequent reanalysis in which P

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TER-C5506-238 Dur-O-Wal was neglected, it was determined that three additional walls needed modification. These modifications included the addition of structural steel bracing at the top of the wall to provide lateral support and the addition of structural steel members across the face of the wall to reduce wall span length. One wall required the elimination of a pipe bearing force at the point where the pipe penetrated the wall. An evaluation of the Licensee's modification methods is provided in Section 3.2.

Thirty walls in the turbine and reactor buildings are subject to pressurization loads in the event of a high energy line break. As part of the reanalysis, the Licensee initiated a study (leak-before-br'eak program) that intended to demonstrate that an instantaneous, open ended, high energy / pipe line break will not occur. Therefore, the pressurization loads caused by a high energy line break were not included in the reanalysis. The Licensee indicated in this study that the probability of an instantaneous pipe failure was so small that it was unnecessary to consider the effects of a high energy line break in the analysis of masonry walls. At present, the NRC staff is reviewing this study to determine the applicability of it to this plant, and the NRC evaluation will be addressed at a later date.

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2. EVALUATION CRITERIA The basic documents used for. guidance in this review were the criteria developed by the Structural and Geotechnical Engineering Branch (SGEB) of the NRC (attached as Appendix A to this report), the Uniform Building Code (7),

and ACI 531-79 [8].

The materials, testing, analysis, design, construction, and inspection of

-safety-related concrete masonry structure should conform to the SGEB criteria.

For operating plants, the loads and load combinations for qualifying the masonry walls should conform to the appropriate specifications in the Final Safety Analysis Report (FSAR) for the plant. Allowable stresses are specified in Reference 8 and the appropriate increase factors for abnormal and extreme environmental loads are given in the SGEB criteria (Appendix A).

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TER-C5506-238

3. TECHNICAL EVALUATION This evaluation is based on the Licensee's earlier responses (2-3] and subsequent responses (4-6] to the NRC requests for additional information.

The Licensee's criteria were evaluated with regard to design and analysis methods, loads and load combinations, allowable stresses, construction specifications, materials, and any relevant test data.

3.1 EVALUATION OF LICENSEE'S CRITERIA The Licensee evaluated the masonry walls using the following criteria:

o The design allowables are based on ACI 531-79 (8].

o The load combinations considered are those defined in the Final Safety Analysis Report (FSAR). .

o The working stress method of analysis was used, o A typical analytical procedure is sununarized below:

- determined wall boundary conditions

- multiply the floor acceleration values from the PSAR by the mass of the wall to obtain an equivalent static force on the wall.

compute stress compare computed stresses with allowable.

'.he Licensee's criteria (5] and responses (4-6] have been reviewed. With the exception of those items identified in Section 4, the Licensee's criteria have been found to be adequate and in accordance with the SGEB criteria (Appendix A).

The following is a review of the Licensee's responses (4) to the NRC's original questions. Questions and responses covering the same topic have been combined.

Question 1

a. Provide and justify the boundary conditions and modeling techniques used for the reevaluation of masonry walls at the Nine Mile Point plant and

b. Indicate how the potential for block pull-out was considered.

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TER-C5506-238 Response la According to' the sample calculations of typical walls provided in Reference 4, the boundary conditions may be either fixed, pinned, or free. A boundary was considered pinned or fixed if it was dowled into the adjacent-concrete structure. A boundary was also considered pinned if it was supported by structural elements such as strap anchors. Walls were modeled as one-way beams or vertical cantilevers (when reinforcing dowels are present at the base).

This response is satisfactory.

Response Ib The Licensee indicated that block pull-out was not a concern because the piping attached to the walls was small in diameter and exerted negligible

! loads.

The essponse is adequate.

Question 2 Indicate how earthquake forces in three directions and equipment loads were considered in the analysis. Using' sample calculations, indicate how the effects of higher modes of vibration are included in the analysis.

Provide the damping values used and justify any deviation,from the SGEB criteria (Appendix A).

Response 2 I In this ret;onse, the Licensee indicated that since no masonry walls at Nine Mile Point Unit I were shear or bearing walls, horizontal in-plane and vertical seismic forces were considered to be negligible. The analysis for horizontal out-of-plane seismic loads.was based on the floor acceleration values that were obtained from the dynamic analysis of the plant buildings.

The floor' accelerations were multiplied by the wall mass to obtain an

! equivalent static load. The Licensee took this approach because the natural wall frequencies were considered high (i.e., the walls were stiff) for an amplified response to occur. The natural frequencies of some sample walls are provided in the table that follows, i

l TER-C5506-238 Wall Wall Nomi-M Boundary Natura'l Example Height (ft) Width (ft) Thickness (in) Conditions Frequency (Hz) 1 20 13 8 4 sides 27.3 pinned 2' 20 13 8 3 sides 29.8 pinned 1 side fixed 3 20 13 12 4 sides 40.7 pinned 4 20 13 12 3 sides 44.4 pinned 1 side fixed As indicated by this table, the natural frequencies of the walls at Nine Mile Point Unit 1 are typically high. Therefore, the rigidity of the walls is such that the response of the walls would not be affected by the amplified portion of the response spectra curve.

The Licensee's response is satisfactory.

Question 3 Provide a brief description and sample calculations to show the analytical approach used for single wythe and multiple wythe walls.

Response 3 In response, the Licensee provided some typical calculations for single and multiple wythe walls. Both single and multi-wythe walls were modeled as i

one-way beam elements or vertical cantilevers (see Response 1). The analysis was carried out using the working stress method as described in the beginning of this Section. The wythes of a multiple wythe wall were assumed to act compositely in flexure because Dur-O-Wal joint reinforcement at every course or every other course ties the wythes together. Also, the Licensee's calcula-tion indicated that for walls up to 92 feet thick, the flexural stress governs over collar joint stress. This value was based on an allowable collar' joint shear of 29.10 psi. However, even if an. allowable of 8 psi were used, all I

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TER-C5506-238 masonry walls would still have thicknesses much lower than the critical value, so flexural stress will govern in all cases. Collar joint shear stress, therefore, was not a consideration in the analysis of masonry walls.

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The Licensee's response is adequate and consistent with the SGEB criteria.

Question 4 Provide and justify the increase factors used in the criteria for allowable stresses. The SGEB criteria allow no increase in the allowable stresses for load combinations including wind or operating basis

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earthquake (OBE) loads. The allowable working stresses for load conditions which represent abnormal / severe and abnormal / extreme environmental conditions such as a design basis earthquake-(DBE) may be multiplied by factors shown in the table in the SGEB criteria which are given below:

Type of Stress Factor Axial or flexural compression 2.5 i

Bearing 2.5  !

l Reinforcement stress except shear 2.0 but not to exceed 0.9 fy Shear reinforcement and/or bolts 1.5 Masonry tension parallel to bed joint 1.5 4

Shear carried by ma,sonry 1.3

, Masonry tension perpendicular to l

bed joint

- for reinforced masonry 0 l - for unreinforced masonry 1.3 4

i Response 4

The Licensee indicated that increase factors were not used in the evaluation of safety-related masonry walls at the Nine Mile Point Unit 1 plant.

This response is satisfactory.

Question 5 Provide sketches of the proposed wall modifications and indicate, using sample calculations, how these modifi. cations will' correct the wall

TER-C5506-238 deficiencies. Indicate the out-of-plane drift effects of the bracing added to walls 31, 44, 45, 59, and 66.

Response 5 A sketch of a typical modification was provided (Appendix B). This modification ~ consists of a series of steel angles attached at one end to an existing steel beam and at the other end to a plate that abuts the top of the wall. This provides lateral support in one direction to the top of the wall.

Existing strap anchors provide the necessary support in the other direction.

Out-of-plane drift effects will not cause overstress because the added bracing does not provide a rigid boundary condition. See Section 3.2 for an evaluation of the Licensee's approach to wall modifications.

Question 6 Provide the status of the proposed wall modification.

Response 6 All wall modifications have been completed.

Question 7 Provide the results of the analysis of all masonry walls in terms of actual stresses versus allowable stresses.

Response 7 l Results were provided for a typical wall. Wall 31 experienced a maximum j -bending compression stress of 138.7 psi compared with an allowable of 231

! psi. The vertical reinforcement tensile stress was 9543 psi compared with an allowable of 20,000 psi (Grade 40 steel). The masonry allowable stress was based on ACI 531-79 and an assumed f'm of 700 psi. Since this initial l

analysis, a test program to determine block and mortar strength has been j completed and the results used in a reanalysis of the masonry walls. In this j test program, three prism samples.were removed from existing walls and tested according to ASTM E-447-74. The test program determined the value of f'm and the mortar strength (m ). The results of the test program are as follows:

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M TER-C5506-238 Minimum. Maximum Average Net Compressive' Strength of Block (psi) 2560 3350 2920

. Prism Strength Based on Net Mortar Area (f'm), 1660 2290 2060 (psi)

Deduced Mortar Strength (mo) 1800 psi Using the average prism strength from the test program, wall 31 has an allowable flexural compression stress of 680-psi instead of 231 psi.

This response is adequate.

Question 8 With reference to the use of Dur-O-Wal reinforcement, the Licensee is requested to provide the following information:

- Provide the technical basis for using Dur-O-Wal as a structural' element.

- Provide assurance for proper anchorage of Dur-O-Wal at boundary and

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proper bonding between Dur-O-Wal and mortar.

- Indicate ntanber of walls qualified by Dur-O-Wal.

- Confirm the existence of.Dur-O-Wal in the walls. (Note: The Licensee indicated that they checked only one wall and found all vertical and horizontal reinforcement as specified in the design.)

Response 8 In response to this request, the Licensee reanalyzed the masonry walls neglecting the presence of Dur-O-Wal and using the masonry strengths obtained from the test program (Response 7). As a result, three walls required

. modification. One modification involved the addition of structural angles at the top of the wall to ensure a pin connection. The other two modifications used steel beams and columns across the wall face to reduce the span length.

~ See Section 3.2 for an evaluation of modifications.

This response is satisfactory and consistent with the SGEB criteria.

TER-C5506-238 3.2 EVALUATION OF LICENSEE'S APPPOACH TO WALL MODIFICATIONS In the Licensee's initial evaluation under IE Bulletin 80-11, six walls did not meet the acceptance criteria and required modifications. Walls 31, 44, 45, 59, and 66 required the addition of bracing at the top of the wall to provide lateral resistance to seismic loads (see Appendix B). Wall 35 did not need structural modification but required the removal of a pipe bearing force where the pipe penetrated the wall.

Following the initial analysis of the masonry walls, a reanalysis was performed neglecting the presence of Dur-O-Wal' joint reinforcement, upon whic's I the initial analysis relied., As a result, it was discovered that three additional walls required modification. One wall used the addition of structural angles at the top of the wall to ensure a pinned boundary support.

f The other two used the addition of steel beams and columns across the wall face to reduce the span length.

The Licensee's approach to wall modifications has been reviewed and has been found to be' adequate and consistent with the SGEB criteria.

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4. CONCLUSIONS A detailed study was performed to provide a technical evaluation of the j . masonry walls at Nine Mile Point Unit 1. Review of the Licensee's criteria and additional information provided by the Licensee led to the conclusions l given below.

The Licensee's criteria have been found technically adequate and in compliance with the SGEB criteria except for the following areas:

o Composite action was assumed for multiple wythe walls. The collar joint shear was evaluated based on an allowable of 29.10 psi, which was derived from the ACI 531-79 [8] formula for shear carried by 4

masonry. This value exceeds the generally accepted collar joint allowables of 8 psi for operating basis earthquake (CBE) and 12 psi for safe shutdown earthquake (SSE). However, as indicated in the review of Response 3 b Section 3.1, flexural stress, governs the analysis of multi-wythe walls in all cases at this plant. Therefore, the collar. joint allowable shear stress does not influence the qualification of masonry walls at Nine Mile Point Unit 1. Also, Dur-O-Wal joint reinforcement in every course or every other course t was used to-tie the wythes together, ensuring composite action.

I o In it's initial analysis of masonry walls under IE Bulletin 80-11, the Licensee neglected to consider the possible pressurization effects of a high energy pipe break on the masonry walls (other applicable loads were considered). Thirty walls in the turbine and reactor buildings are subject to pressurization loads in the event of a high energy line break. As part of the subsequent reanalysis, the Licensee initiated a

" leak-before-break" program to show that an instantaneous, open ended, high energy line break will not occur. If the re'sults of this program

are valid, then the neglect of pressurization loads due to a high energy pipe break is justified. At present, the NRC staff is

! reviewing this issue to determine the applicability of this study to this plant, and the NRC evaluation will be addressed at a later date.

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With regard to wall modifications, nine walls required modification in order to meet the SGEB acceptance criteria. These modifications included the addition of bracing at the top of the wall to provide lateral seismic l resistance and to ensure a pinned support and the addition of steel beams and columns across the wall face to reduce the span length. One wall (35) f required the removal of a pipe bearing force at the point where the pipe penetrated the wall. These approaches to wall modifications have been reviewed and are considered adequate. All modifications have been installed.

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REFERENCES

1. Masonry Wall Design NRC, 08-May-80 IE Bulletin 80-11

2. T. E. Lempges Letter to B. H. Grier (NRC)

Subject:

Nine Mile Point Unit 1, IE Bulletin 80-11, Response to Items 1, 2a and 3 Niagara Mohawk Power Corporation, 08-Jul-80

3. T. E. Lempges Letter to B. H. Grier (NRC)

Subject:

Nine Mile Point Unit 1, IE Bulletin 80-11, Item 2b, Re-evaluation of Masonry Walls Niagara Mohawk Power Corporation,10-Nov-80

4. T. E. Lempges Letter with Attachments to D. B. Vassallo (NRC)

Subject:

Additional Information Regarding Response to IE Bulletin 80-11 Niagara Mohawk Power Corporation, 14-June-82

5. C. V. Mangan Letter with Attachments to D. B. Vassallo (NRC)

Subject:

Design Criteria for Reanalysis of Safety-Related Masonry Walls Niagara Mohawk Power Corporation, 24-June-82 5,

6. T. E. Lempges Letter with Attachments to D. B. Vassallo (NRC)

Subject:

Additional Information Regarding Masonry Wall Keanalysis and Test Program ,

! Niagara Mohawk Power Corporation, 21-June-82 ;

7. Uniform Building Code International Conference of Building Officials, 1979

8. Building Code Requirements for Concrete Masonry Structures Detroit: American Concrete Institute, 1979 ACI 531-79 and ACI 531-R-79 e

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e APPENDIX A SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH

[SGEB] OF THE NBC)

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FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN 20tt11 RACE STREETS,PHILADELP,41 A,PA 19105

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CONTENTS Section Title Page 1 GENERAL REQUIREMENTS . . . . . . . . . . . A-1 2 LOADS AND LOAD COMBINATIONS. . . . .- . . . . . A-1 a .- Service Load Combinations . . . . .. . . . . A-1

b. Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions . . . . . . . . . . . . . A-2 3 ALLOWABLE STRESSES . . . . . . . . . . . . A-2 4 DESIGN AND ANALYSIS CONSIDERATIONS . . . . . . . . A 5 REFERENCES . . . . . . . . . . . . . . A-4 d

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1. General Requirements The materials, testing, analysis, design, construction, and inspection related to the design and construction of safety-related concrete masonry walls should conform to the applicable requirements contained in Uniform Building Code - 1979, unless specified otherwise, by the provisions in this criteria.

The use of other standards or codes, such as ACI-531, ATC-3, or NCMA, is also acceptable. However, when the provisions of these codes are less conservative than the corresponding provisions of the criteria, their use should be justified on a case-by-case basis.

In new construction, no unreinforced masonry walls will be permitted. For

• operating plants, existing unreinforced walls will be evaluated by the provisions of these criteria. Plants which are applying for an operating license and which have already built unreinforced masonry walls will be evaluated on a case-by-case basis.

2. Loads and Load Combinations The loads and load combinations shall include consideration of normal loads, severe environmental loads, extreme environmental loads, and abnormal loads. Specifically, for operating plants, the load combinations provided in the plant's FSAR shall govern. For operating license applications, the following load combinations shall apply (for definition of load terms, see SRP Section 3.8.4II-3).

(a) Service Load Conditions (1) D + L' (2) D+L+E (J) D+L+W If thermal stresses due to To and Ro are present, they should be included in the above combinations as follows:

(la).D + L + To+Ro (2a) D+L+To+Ro+E (3a) D + L + To+Ro+W Check load combination for controlling condition for maximum 'L' and for no 'L'.

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TER-C5506-238 (b) Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions (4) D+L+To+Ro+E (5) D + L + To+Ro+Wt  ;

(6) D+L+Ta + R + 1.5_Pa (7) D + L + Ta+Ra + 1.25 Pa + 1.0 (Yr + Yj + Ym) + 1.25 E (8) D + L + Ta+Ra + 1.0 Pa + 1.0 (Yr + Yj + Ym ) + 1.0 E'

In com.binations (6), (7), and (8) the maximum values of Pa,' T ea Rea Yje Y r, and Y m, including an appropriate dynamic load factor, should be used unless a time-history analysis is performed to justiff otherwise. Combinations (5), (7), and (8) and the

corresponding structural acceptance criteria should be satisfied first without the tornado missile load in (5) and without Yr

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. and Y,in (7) and (8). When considering these loads, local section strength capacities may be exceeded under these concentrated loads, provided there will be no loss of function of any safety-related system.

Both cases of L having.its full value or being completely absent should be checked.

3. Allowable Stresses Allowable stresses provided in ACI-531-79, as supplemented by the '

i following modifications / exceptions, shall apply.

(a) When wind or seismic loads (OBE) are considered in the loading combinations, no increase in the allowable stresses is permitted.

(b) Use of allowable stresses corresponding to special inspection l category shall be substantiated by demonstration of compliance with the inspection requirements of the SEB criteria.

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l (c) When tension perpendicular to bed joints is used in qualifying the unreinforced masonry walls, the allowable value will be justified by test program or other means pertinent to the plant and loading conditions. For reinforced masonry walls, all the tensile stresses will be resisted by reinforcement.

(d) For load conditions which represent extreme environmental, abnormal, abnormal / severe environmental, and abnormal / extreme environmental conditions, the allowable working stress may be multiplied by the factors shown in the following table:

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TER-C5506-238 Type of Stress Factor Axial'or Flexural Compression 2.5 Bearing 2.5 Reinforcement stress except shear 2.0 but not to exceed 0.9 fy Shear rei M orcement and/or bolts 1.5 Masonry tension parallel to bed joint 1.5 Shear carried by masonry . 1.3 ,

Masonry tension perpendicular to bed joint for reinforced masonry O for unreinforced masonry2 1,3 Notes (1) When anchor bolts are used, design should prevent facia'l spalling of masonry unit.

(2) See 3(c).

4. Design and Analysis Considerations (a) The analysis should follow established principles of engineering mechanics and take into account sound engineering practices.

. (b) Assumptions and modeling techniques used shall give proper considerations to boundary conditions, cracking of sections, if ant, and the dynamic behavior of masonry walls.

(c) Damping values to be used'for dynamic analysis shall be those for reinforced concrete given in Regulatory Guide 1.61.

(d) In general, for operating plants, the seismic analysis and Category I structural requirements of FSAR shall apply. For other plants, .

corresponding SRP. requirements shall apply. The seismic analysis shall account for the variations and uncertainties in maso, materials, and other pertinent parameters used.

(e) The analysis should consider both in-plane and out-of-plane loads.

(f) Interstory drift effects should be considered.

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(g) In new construction, grout in concrete masonry walls, whenever used,

, shall be compacted by vibration.

(h) For masonry shear walls, the minimum reinforcement requirements of ACI-531 shall apply.

(i) Special constructions (e.g., multiwythe, composite) or other items not covered by the code shall be reviewed on a case-by-case basis for their acceptance.

i (j) Licensees or applicants shall submit QA/QC information, if available, for staff's review.

In the event QA/QC information is ndt available, a field survey and a test program reviewed and approved by the staff shall be implemented to ascertain the conformance of masonry construction to design drawings and specifications (e.g., reber and grouting).

(k) For masonry walls requiring-protection from spalling and scabbing due to ac%ident pipe reaction (Y r), jet impingement (Y.j), and missile impact (Ym), the requirements similar to those of SRP 3.5.3 shall apply. .However, actual review will be conducted on a case-by-case basis.

5. References (a) Uniform Building Code - 1979 Edition.

(b) Building Code Requirements for Concrete Masonry Structures ACI-531-79 and Commentary ACI-531R-79.

(c) Tentative Provisions for the Development of Seismic Regulations for Buildings - Applied Technology Council ATC 3-06.

i (d) Specification for the Design and Construction of Load-Bearing Concrete Masonry - NCMA August, 1979.

(e) Trojan Nuclear Plant Concrete Masonry Design Criteria Safety Evaluation Report Supplement - November,1980.

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APPENDIX B SKETCH OF TYPICAL WALL MODIFICATION E

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